A method was developed to measure the rate of incorporation of palmitate, Jpalm, from plasma into different brain regions in the awake rat. A theoretical model was developed to calculate Jpalm from data. The distribution of (14C)palmitate in biochemically separated brain fractions indicated that the radioactivity being measured in the autoradiograms is predominantly in lipid molecules found in membranes. Phosphatidyl choline contains the greatest amount of total lipid label. Jpalm did not change with aging in Fischer-344 rats between 3 and 34 months of age, indicating that the rate of turnover of palmitate-containing brain lipids was age-invariant. Jpalm was reduced in central auditory pathways following chronic damage to the cochlea. Several days following a 5-minute period of bilateral ischemia, gerbils had reduced palmitate incorporation into the irreversibly damaged CAl region of the hippocampus but increased incorporation into recovering regions such as the CA3 and dentate gyrus. Palmitate incorporation into the hypoglossal nucleus increased maximally 24 days after hypoglossal nerve axotomy. This increase correlated with nerve regeneration. Following axotomies in which regeneration was prevented, palmitate incorporation remained decreased between 24 and 35 days.